Precise elucidation of the blood group M and N immunodeterminants and their precursors T and Tn is our goal to establish the significance of the T antigen in human respiratory, gastrointestinal tract and breast adenocarcinoma in view of the profound cellular and humoral immune response which patients with such carcinomata but not healthy persons, and generally not patients with benign disease show against T antigen. Starting materials are a) The homogeneous highly active NH2-terminal sialoglycopentapeptides we have prepared from larger human MM and NN erythrocyte-derived Alpha-1 glycopeptides. b) Lipidic extracts of normal guinea pig tissue sent by Dr. John L. Cantrell of NIAID which we found to contain M-, N- specific structures, and lipidic extracts of a guinea pig carcinoma possess Tn, T and N receptors in reactive form. c) Human breast carcinoma cell membrane fractions obtained from tissue culture cells of MCF-7 carcinoma. We found these cells to possess extensive M, N, T and Tn activities. Preparative studies will be guided by assessment of biological activities. We will cleave the glycosidically-linked oligosaccharide chains of the active materials by Beta elimination. We will prepare homogeneous active oligosaccharides. Their structures will be determined by standard modern and classical techniques of carbohydrate chemistry.